Cards with magnetic strips have become commonplace. Credit cards are a common and widely distributed form of card having a magnetic strip. On the magnetic strip of a credit card is stored information relating to the credit card such as information shown on the front of the card. This allows entry of credit card information by a simple "swipe" of the credit card through a magnetic strip reader. Because of their programmability, low cost, and simplicity of use, storage of information on magnetic strips is popular. For example, cards having magnetic strips are now used in doorway access applications, credit cards, INTERAC cards, identification cards and so forth.
Unfortunately, those same features that make the use of cards having magnetic strips thereon so widespread also limits their use. For example, ease of writing and reading magnetic strip information makes it undesirable to store confidential information on a magnetic strip. Also, it is difficult to increase security of doorways accessed by magnetic strips. The problem is exemplified by the ease with which credit cards are stolen and used by unauthorised users.
Many methods of avoiding these problems are known. Most of these methods relate to two particular problems. Both these problems relate to fraudulent use of a card. For example, some cards with magnetic strips are provided with a picture of an authorised user of the card. This allows someone accepting the card to visually verify that the user of the card is authorised to do so. For credit cards and for business doorways where security staff are already present this is very useful. Unfortunately, absent a human to verify the user and the image on the card, no improved security results. Another form of fraud prevention encodes a card with a counterfeit protection image or code. These are commonly seen on credit cards and often take the form of a hologram. Again, the counterfeit prevention hologram must be verified by a person. Though fraud prevention is an important aspect of credit card use and distribution, it does not address the need to provide privacy of information contained on a magnetic strip.
Reading and writing information to magnetic tape is well understood. Magnetic tape is used for audio recording, video recording, data storage, and magnetic strips. A review of technical knowledge relating to magnetic tape is available in The Complete Handbook of Magnetic Recording 4th Edition By Finn Jorgensen McGraw Hill 1996 which is hereby incorporated by reference.
In U.S. Pat. No. 5,777,903 for a Solar Cell Powered Smart Card with Integrated Display and Interface Keypad issued to Piosenka et al. on Jul. 7, 1998 and hereby incorporated by reference, a solar powered smart card is disclosed. The use of solar power is advantageous for portable devices as is well known. The invention allows a smart card that incorporates its own power source.
It would be advantageous to provide a secure magnetic strip that can not be read absent authorisation.